United States Senator Ted Cruz reaffirmed his ultimatum yesterday to seek to impose sanctions on specific Cambodian officials “as an initial response” to the jailing of opposition leader Kem Sokha unless Sokha is immediately released.

The former US presidential hopeful first called on the Cambodian government to release Sokha by the end of the National Election Committee’s voter registration period, which closed yesterday, in a letter to Cambodian Ambassador Bun Rong last month.

Rong responded in a letter to Cruz on Tuesday, asking the senator to “view the current situation in Cambodia from our perspective”.

In his letter, Rong compares Sokha to Paul Manafort, the former campaign chairman for Donald Trump who was recently charged with tax fraud and money laundering, and says Sokha’s actions are similar to crimes listed in the US Espionage Act.

“It is not fair that the Cambodian Government is criticized and threatened with punitive action for taking legal action to protect its own security, peace, independence and sovereignty, just as any other nations would do,” Rong’s letter said.

In a press release yesterday, Cruz slammed the ambassador’s words as “dismissive excuses and empty platitudes”.

If the opposition leader is not released and radio stations not allowed to resume broadcasting, “it will be impossible for the United States and our allies to recognize the legitimacy of these elections”, Cruz’s statement reads, referring to next year’s vote.

Asked whether the Kingdom was worried about US sanctions, government spokesman Phay Siphan said finding people who commit treason “is the priority”.

“[Cruz] is a stranger to Cambodia. He has no right, he has no power to order Cambodia to do this, to do that,” Siphan said.

“He could do everything he likes. Go ahead and do it. Cambodia’s a sovereign state, and we are just trying to get rid of treasonous persons.”

Cruz could not be reached yesterday. He is one of a handful of US politicians – among them senators John McCain and Dick Durbin – who have spoken out about the government’s crackdown on the opposition.

Kem Monovithya, daughter of Sokha and the CNRP’s deputy director-general of public affairs, said yesterday that she has been in communication with Cruz, McCain and others about targeted travel and financial sanctions for Cambodian officials. “It’s time to start applying those pressures,” she said.